Step-by-step to baking a model for export, so that it looks smooth but doesn't have all the faces of a subdivided mesh
Baking can be used to create the image texture for example a character. It can also be used to create normal maps. The below video teaches how to remove faces from a high poly mesh but still keep the detail in it by simply adding a normal.
https://www.youtube.com/watch?v=ApzVWuPa4A4